Dynamic balancer



SePt261944 J. G. WILLIAMS 2,359,180.

DYNAMIC BALANCER Fi'ledAug. 11, 1942 2 Sheets-Sheet 1 'nventor Patenterlsept. 2.61944 y* j Motors Corporation, Detroit, Mich, ai 'Y col'lul'ltioll ffnelm Application Augusta, 1942, sensi No. 454,439

4 Claims.

This invention has to `do with dampers for elim- -inating tcrsionalvibrations and particularly with dampers of the centrifugal pendulum type used on crankshafts of internal combustion engines.

Such dampers act as pendulums, the restoring 5 sists essentially of'a weight pivoted to the end of force being centrifugal force instead of gravity a link, the weight being provided 'with guiding as in the case of the ordinary pendulum. They means so that in swinging all points `on the weight are characterized by the factthat the number of will move along arcs of the same length and raswings of the pendulum per revolution of the shaft dius. Were guiding means not provided the penisconstant at all speeds of rotation. dulum would be less effective in that it would It has also long been known that the number of not be performing a substantially pure pendulum swings of a centrifugal pendulum during each movement. Furthermore there would be nothing revolution of the shaft varies directly as -the to prevent the pendulum from striking the shaft square root ofthe' ratio between the distance at the ends-*of its swing, particularly at the low from the center of the sliaft to the fulcrum of speeds and upon starting when the centrifugalV 'the pendulum and the length of the pendulum. force is low. 'Ihe damper is. of course, designed This relation is expressed mathematically by the s0 as to permit it to perform' its pendular moveformula o ment rather than stick ,and fail to swing and to R accomplish this is preferably provided with antin= L- frictionor'other good bearings at its pivotsand h in its guiding means. l w ere o In the drawings: y l

n=number of swings of the pendulum during each Figure 1 is a View partially in llongitudinal secrevolution of the shaft; i tion showingthe application of the improved R=fthe distance from the center of the shaft to damper to one end of the crankshaft of an inter-` the fulcrum of the pendulum, and nal combustion engine. The view is taken sub- L=ithe length of the pendulum-that is, the disstantially on line Il '0f Figure `2- tance from the pivot of the pendulum to Figure 2 is a view taken online 2-2 of Figure 1 its center of gravity. Y with parts broken away. A an example of the operation of a centrifugal ofifeis a section taken along the ne of 3 3 pen ulum damper, if a crankshaft is provided with such a damper designed to make four comrsea sectlon taken along the Ime gf niii teifi am@ 51S a View on une 5-5 of Figure 1- g In the speciiic embodimenL of my invention impulses during each revolutionas for example, h '1 lo i by explosions in four diiierent cylinders of the s own' m Figure indicates 0ne.end of the ankshaft of an internal combustion engine. engine duringeach revolution-the four twists cg m by me essereessereessere each revolution are neutralized by the pendulum 40 I6 of the crankgasein the lsual manner Journal swingingfour times each revolution in a direction n is( referabl bor d out to edu itsvei ht and to tend to twist the vshaft in the opposite dlrecp y e ce o g non is Provided with an integral end lzange I8 interr 'A me e te assistiti?.transiti., einem number of twisting impulses during each revo f8 is secured plate Z2by means of suitable bolts muon is 10W form that case the Pendulum must and nuts indicated et 24; Plate '22 is preferably be designed t0 Swing but few ms Per M0111- provided with internal splines as indicated at 2s tion. A centrifugal pendulum designed for a adapted to mesh with external splines 28 on a Small number 0f Swings Per revolution must be stub or extension shaft 30 which may be provided comparatively long with respect to the distance with gears as indicated at 32 for driving the en` from'the center of the shaft to its fulcrum: that gine auxiliaries, such as the generator, super 18.1 of the equation must be long with respect charger and the like. toR. At points 120 apart theplate 22 is provided The improved centrifugal 'pendulum damper n with radial extensions 34 apertured as indicated l disclosed m this application ls espeeieuy adopted (Ci. i4-574) l to neutralize twisting impulses ,occurringa very few number of times per revolution,'for example one and one-half times per revolution in the case of a particular twelve cylinder V engine. It con at 36 to receive pins I8 on which are hung pendulum dempers 40. The pins 38 are provided at one end with flanges 42 to limit their- -movement in one direction while movement in the other direction is prevented by stampings 44, one of which is shown in Figure 5, bolted or otherwiseV rigidly secured to the flange I8 on the end of the crankshaft. The type of pendulum damper just described is well known and its operation will be understood by those skilled in the art.

Between centrifugal pendulum dempers 4u are secured the improved dempers embodying my invention. These dampers consist essentially cfa weight 46 suspended from the plate 22 by means of a swinging link assembly 48. In the specific embodiment shown the link assemblies consist of plates 50 apertured at their ends to receive bolts or pivot pins 52. The outer bolt 52 passes through an aperture provided in the lpendulum 54 and is surrounded by an inner race or spacer 56. A series of needle bearing .rollers 5t is provided between the sleeve 56 and the interior of the aperture in the damper weight. Passages 59 are prof -bearing is likewise provided to receive this bolt,

the bearing consisting of an inner race or spacer tt, and an outer race tt, together with needle bearing rollers 58 between the races. Thefouter bearing race 6D is preferably provided with a flange w at one end provided with an oil passage as shown to permit lubricant to reach the needle bearings. It is to provide clearance for the pivot just described that the flange lil or the crankshaft is cut away at the points ril.

The opposite ends of the damper weight are slotted as vindicated lat it and the resulting flanges are apertured as indicated at 'i2 to receive spindle 'i4 on which is mounted roller it preferably provided with a suitable bushing it. Roller and bushing are apertured as indicated to permit oil to reach the bearing surfaces.

The rollers 'It engage cam guide surfaces il@ formed on the 4plate 22. 'Ihecurvature of the surfaces t@ is such that throughout its arc of swing all points on the damper weight move along arcs of the same length and radius. It has been determined that the radius of the cam guide surfaces should be equal to the length L of the pendulum minus the radius of the roller 7E. The

ing of the shaft due to the torsional impulses to such an extent that when one of a series of impulses tuned to the same frequency per revolution as the dampertends to twist the shaft in one direction, the damper weight will react through the link and tend to twist it inthe other direction therebyl more or less neutralizing the effect of the impulse.

It will be noted that-inasmuch as lcentrifugal force is tending to move the weight 46 outwardly pivots 52. In the case of the4 damper indicated at it the pendulum length is equal to the distance between the diameter of the roller 38 and the diameter of the apertures in which it is received. It is obvious that if an effort were made to employ this construction for a pendulum of considerable length the result would be to very greatly increase the size of the apertures with resultant weakening of the construction.

While I have indicated provision for lubrication by oil thrown from the bearings and splashed about in the crankcase, provision may be made for force feed lubrication of the damper pivots and rollers if desired.

My improved damper has perfumed very satisfactorily in actual service in ,high powered aviation engines.

While I have shown the improved dampers arranged in the same plane and symmetrically centers of the. cam guide surfaces 8i) are indicated at C. It will be noted that with the damper in mid position the lines connecting the centers C with the centers of the rollers 1B are parallel with the line passing through the centers of the crankshaft and the centers of the bolts weight, the latter will be set oscillating andl'will swing -back and forth on the link, assuming in extreme cases the position indicated by dotted.

lines at the upper right hand part of Figure 2.

Actually at the operating speeds of the highpowered aviation engines with which this damper is used, the amplitude of swing will be much less than indicated. The swinging of the damper weight back and forth will lag behind the twistdisposed about the shaft axis so that they are dynamically and statically in balance, if desired but one may be used. In such event it should take the place of ne of the usual counterweights so as not to disturb the balance of the shaft.

It will be understood, of course, that where a number of dampers is employed as in the form illustrated, the spacing of them about the shaft axis will depend upon the number of cylinders type of crankshaft the spacing would be and so on.

In some instances it may be found desirable to replace the needle bearings 58 with plain bearings, preferably of material such as silver, with or without a thin lead coating, or copper-lead alloy, having not only good frictional properties but also relatively high compression strength to enable it to carry heavy loads. Where plain bearings are employed force feed lubrication may be used, if desired.

In designing my improved balancer, it will be found that good results may be obtained without taking into account in the computation the inertia of the links 50 as this factor appears to have a negligible effect on tuning where, as in this design, the mass of the links is relatively low compared to the mass of the swinging weights. If heavy links are used their weight is a factor in determining the value of L in the formula.

I claim:

1. In a'torsional vibration damper the combination of a rotatable shaft having a link eccenand cooperating guiding means on the shaft and weight, said link being of such length that the pivots are spaced apart a distance greater than the sum of the radii of the pivot bearings, where-l trically pivoted thereto, -a weight pivoted at itsl y center of gravity to the opposite end of the link,

stantlally free from the action of centrifugal l force.

2. In a torsional vibration damper the combination of a rotatable shaft having a link eccentrically pivoted thereto on an axis substantially parallel with the shaft axis, a weight pivoted at its center of gravity at the opposite end of the link, and cooperating guiding means on the shaft and weight, said link being of such length that the pivots are spaced apart a distance greater menthe sum nf the radii cf the pivot bearings, vwhereby swinging movement of all points on the weight is. confined to arcs of the same length and radius, said guiding means comprising antiiriction rollers rotatably mounted at the ends of the weight and curved guideway's on the shaft engaging the rollers, said guideways lying radially inward of the rollers. v

3. In a torsional vibration damper the comb1 spaced about its axis for independent movement in radial planes, a weight pivoted at approximately its center of gravity to the opposite end of each of said links, guiding means on the shaft, guiding means on each of said weights cooperating with the guiding means on the shaft,

each'oi said links being of such length that its v pivots are spaced apart a distance greater than the sum of theradii of its pivot bearings, whereby swinging movement of all points on the weight is confined to arcs of the same length and radius, said guiding means including rotatable antifriction rollers engaging a' track .substantially free from the loading action of centrifugal force.

4. In a torsional vibration damper, the combination of a shaft having a flange thereon, a weight, a pair of links each pivotally connected vat its inner end to the flange and at its outer end to the weight at approximately its center of gravity, each of said links being of such. length that its pivots are spaced apart a distance greater than the sum of the radii of its pivot bearings, and rollers pivotally mounted on the ends of the weight engaging cam surfaces on the flange, said cam surfaces lying radially inward of the rollers. whereby swinging movement of all points on said weight is confined to,I arcs of the same length and' radius.

JOHN G. WILLIAMS. 

